Paracetamol: A History of Assumptions, Errors, and Evidence Reversals in Pain Management

Paracetamol (acetaminophen) is among the most widely used medications in the history of humanity for treatment of pain conditions. For more than half a century, it has occupied a unique position as the archetypal first-line analgesic and antipyretic, recommended across age groups, clinical settings, and healthcare systems. Its remarkable success has been based on three fundamental assumptions: it is effective for common painful conditions, substantially safer than alternative analgesics, and suitable for broad population use with minimal restrictions. Over the last two decades, however, these assumptions have been increasingly challenged by accumulating evidence from randomized trials, systematic reviews, pharmaco-epidemiological studies, and regulatory analyses.

The history of paracetamol represents an instructive example of evidence reversal in modern medicine and pain management. Originally introduced as a safer successor to phenacetin, paracetamol benefited from a favorable safety reputation that often exceeded the available scientific evidence. Subsequent investigations have revealed a more complex reality. Hepatotoxicity has emerged as a leading cause of acute liver failure worldwide, efficacy in chronic musculoskeletal disorders has proved substantially lower than previously assumed, and concerns regarding long-term safety and use during pregnancy have generated ongoing scientific debate. Simultaneously, clinical practice and prescribing habits remained largely unchanged despite evolving evidence and repeated modifications of international guidelines. By examining major assumptions, scientific misconceptions, regulatory decisions, and evidence reversals, this review explores how one of medicine's most familiar drugs in pain medicine became a paradigm of the challenges inherent in translating evolving scientific evidence into clinical practice. Beyond paracetamol itself, this story provides broader lessons regarding therapeutic inertia, medical dogma, risk perception, and the dynamic nature of evidence-based medicine.